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A licensee-identified violation was discov … A licensee-identified violation was discovered on May 11, 2010 for Unit 1 and Unit 2 of TS 3.7.4 which states, two main control room environmental control (MCREC) subsystems shall be operable during MODES 1, 2, and 3, during movement of irradiated fuel assemblies in the secondary containment, during core alterations, or during OPDRVs. Contrary to this requirement, during performance of a TS SR 3.7.4.4 per licensee procedure 42SV-Z41-003, Control Room Filter Train Flow and DP Measurement, it was identified that the acceptance criteria could not be met. Specifically, the requirement for each MCREC subsystem to maintain a positive pressure greater than or equal to 0.1 inches water gauge relative to the turbine building was not met. According to the licensees cause determination report, this procedure confirmed that the main control room pressurization function was not single-failure proof because of a design change implemented in 1984. The design change added a womens restroom within the main control room envelope and installed single dampers in the exhaust of the mens restroom (1Z41-F019) and the womens restroom (1Z41-F020). Prior to this design change, the main control room had one restroom with redundant dampers in the exhaust ventilation. Since the F019 and F020 dampers are normally open, an inoperable main control room boundary has existed for longer than allowed by TS requirements. Upon discovery of this condition, the licensee entered the TS required action to restore the main control room boundary within 24 hours by closing the 1Z41-F019 and 1Z41-F020 ventilation exhaust dampers. A subsequent test was performed with both dampers closed that fully met the pressurization function acceptance criteria. The significance of this finding was screened using the Phase 1 of the SDP in accordance with NRC IMC 0609 Attachment 4, Table 4a. The analysis determined the significance of the finding to be Green, because the finding only represented a degradation of the radiological barrier function provided for the control room. This issue was captured in the licensees corrective action program as CR 2010106225 and was documented in LER 05000321,366/2010-003as documented in LER 05000321,366/2010-003
23:59:59, 30 September 2010 +
23:59:59, 30 September 2010 +
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15:40:33, 30 May 2018 +
23:59:59, 30 September 2010 +